The present invention relates to a method and apparatus for achieving the complete combustion of gases coming from certain combustion reactions, and more particularly to such a method and apparatus using an "afterburner" or secondary combustion chamber.
At present, a number of combustion processes are carried out in which both the intended fuel and pollutants take part in and undergo combustion to a greater or lesser degree. Afterburners have long been used on jet engines for aircraft, although not for the purpose of achieving complete combustion of aviation fuel for environmental reasons but rather in order to attain higher performance. Exhaust emission control devices for motor vehicle engines are not really afterburning devices but rather arrangements for recirculating the exhaust gases.
In the case of incinerators for refuse, destructors and process furnaces in industry, as well as heating boilers, combustion is carried to a stage comprising a balance between what is economical in terms of a return on the process and what is required by the environmental protection authorities. A common method of reducing the degree of pollution in the emissions is to use a flue gas filter or flue gas scrubber. However, the problem of disposing of what has been collected in the filters or scrubbing fluids still remains. A conventional method of reducing the degree of pollution in the nearby environment is to use tall chimneys to send the pollutants up for dilution in the higher atmospheric layers. The effect of such measures is becoming increasingly apparent in Scandinavian forest areas where sulphurous acid from tall chimneys at incineration plants on the Continent rains down. The operating philosophy at destructors and refuse incineration plants has mostly been to reduce the concentration of malodorous substances in the flue gases. To the extent that tall chimneys have proved inadequate the incinerators have therefore been operated at nighttime when few people are out and about. The same procedure has long been adopted to crematory funaces--for ethical reason.
From the foregoing, it will be evident that numerous incineration plants exist where it is desirable to reduce the content of pollutants in the flue gases. In the combustion of household refuse alone it is possible to trace some 50 substances, stemming from different plastic materials, in the flue gases. By means of the present invention it is possible to convert the vast majority of these to water vapor and carbon dioxide.
The object of the present invention is to provide a method and a device for transforming unburned flue gas components from incineration plants into harmless substances by means of afterburning.